| Yangla copper deposit in Yangla,Deqin County,Yunnan province,is adjacent to the East Tibet and the West Sichuan provinc.The mine has become the largest copper-polymetallic deposit in the Sanjiang copper-polymetallic ore belt, whose origin has cause great interest in the field of metallogeny,and many perspective have been made.In this paper,on the basis of previous studies,Linong massive sulphide deposit is the main research subject and the author use geochemistry, mineralogy, metallogeny, etc.as the main theory to study the origin of the Yangla copper deposit. And the results are as follows.1, Yangla granodiorites are at the age of 215 to 238Ma.The isochron age of molybdenite Re-Os, in the may vein,which pierce the KT2 and KT5 stratiform massive sulphide ore body,is 228.3+ 3.8Ma and 230.0+4.8Ma.And the age is the same as the granodiorite,indicating that the massive sulphide ore body in the early Devonian strata of the Yangla copper deposit had been reformed by the magama of the Indosinian stage.2, There are great many inclusions in Linong deposit,and the gas-liquid two-phase inclusions can often be seen,whose size generally extend between 5 and 20μm, and the shape is mostly negative crystal, long cylindrical, irregular shape, small round granular and so on.These inclusions arrange intensively in different directions and the gas-liquid ratio of the inclusions is at around 10%. The uniform temperature of the inclusions is between 165 and 302, and the average temperature is 232.The inclusions in the wallrock are also very plentiful,which are gas-liquid inclusions and arrange intensively in different directions and the gas-liquid ratio is at around 10%. The size of the inclusions extend between 4 and 18μm。The shape of the inclusions usually present strip-like,long cylindrical,oval-shped, small roud granular, irregular-shape and so on. The uniform temperature of the inclusions is between 125 and 212, and the mean value is 193.These indicate that the main metallogenetic phase of the stratiform massive sulphide ore body in the Linong deposit is at low temperature stage.3, The wallrock of the ore body is mostly slate containing chlorite,the content of the SiO2 in which extends between 28.45% and 71.34%,most of the content extending between 45% and 65%, and some samples are greater than 65%, belong to the intermediate-basic rock.When constructing the graphic to restore the content of the original rock,the most samples project onto the volcanic zones. These show that the ore-bearing rocks is metamorphic intermediate-basic volcanic rocks.4, Based on the previous studies,and in the light of the tectonic settings,the shape and the attitude of the ore body(mostly layered,layer-like,and also irregular-shaped produced in the contact zone),the structure and the tecture of the ore (colloid,gelatinous structure and massive,striated layer and a variety of replaced and alterated structure), the ore-forming chronology,the fluid inclusion studies and the stable isotope composition,Yangla copper deposit experienced SEDEX in Hercynian stage and reconstructed ore-forming process of the magmatic hydrothermal in Indosinian stage. Yangla copper deposit is a volcanic deposition-transformation of magmatic deposit with complex geneses. |
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